The objective of the research project is to investigate and analyze a variety of information-processing mechanisms in monkeys, i.e., stimulus encoding, selective attention, and selective retention. Where feasible, coordinate studies will be conducted with pigeons. Most of the experiments, which are long term, employ the matching paradigm, both identity and conditional matching, and some will use multiple sample inputs. A major goal of the experiments is to allow us to specify more precisely than currently is possible some of the basic differences in the information-processing capacity of primates and pigeons, and to relate these findings to human cognitive processes.